GEMPAK Manual
GEMPAK PARAMETERS
This appendix contains a list of the GEMPAK parameters.
Algorithms used in computing these parameters are also included.
The following constants are used in the computations:
KAPPA = Poisson's constant = 2 / 7
G = Gravitational constant = 9.80616 m/sec/sec
GAMUSD = Standard atmospheric lapse rate = 6.5 K/km
RDGAS = Gas constant for dry air = 287.04 J/K/kg
PI = Circumference / diameter = 3.14159265
References for some of the algorithms:
Bolton, D., 1980: The computation of equivalent potential
temperature., Monthly Weather Review, 108, pp 1046-1053.
Miller, R.C., 1972: Notes on Severe Storm Forecasting
Procedures of the Air Force Global Weather Central,
AWS Tech. Report 200.
Wallace, J.M., P.V. Hobbs, 1977: Atmospheric Science, Academic
Press, 467 pp.
TEMPERATURE PARAMETERS
TMPC - Temperature in Celsius
TMPF - Temperature in Fahrenheit
TMPK - Temperature in Kelvin
STHA - Surface potential temperature in Kelvin
STHK - Surface potential temperature in Kelvin
STHC - Surface potential temperature in Celsius
STHE - Surface equivalent potential temperature in Kelvin
STHS - Surface saturation equivalent pot. temperature in Kelvin
THTA - Potential temperature in Kelvin
THTK - Potential temperature in Kelvin
THTC - Potential temperature in Celsius
THTE - Equivalent potential temperature in Kelvin
THTS - Saturation equivalent pot. temperature in Kelvin
TVRK - Virtual temperature in Kelvin
TVRC - Virtual temperature in Celsius
TVRF - Virtual temperature in Fahrenheit
THTV - Virtual potential temperature in Kelvin
TDXC - Maximum 24 hour temperature in Celsius
TDNC - Minimum 24 hour temperature in Celsius
TDXF - Maximum 24 hour temperature in Fahrenheit
TDNF - Minimum 24 hour temperature in Fahrenheit
T6XC - Maximum 6 hour temperature in Celsius
T6NC - Minimum 6 hour temperature in Celsius
T6XF - Maximum 6 hour temperature in Fahrenheit
T6NF - Minimum 6 hour temperature in Fahrenheit
DMAX - Daily weather map maximum temperature in Fahrenheit
DMIN - Daily weather map minimum temperature in Fahrenheit
SSTC - Sea surface temperature in Celsius
SSTF - Sea surface temperature in Fahrenheit
LTMP - Temp. in Celsius of surface air lifted to 500 or !x mb
TMPC = ( TMPF - 32 ) * 5 / 9
TMPC = TMPK - 273.16
THTA = TMPK * ( 1000 / PRES ) ** KAPPA
STHA = TMPK * ( 1000 / PALT ) ** KAPPA
TVRK = TMPK * ( 1 + ( .001 * MIXR ) / .62197) ) /
( 1 + ( .001 * MIXR ) )
THTV = TVRK * ( 1000 / PRES ) ** KAPPA
THTE = THTM * EXP [ ( 3.376 / TLCL - .00254 ) *
( MIXR * ( 1 + .81 * .001 * MIXR ) ) ]
THTM = potential temperature for moist air
= TMPK * ( 1000 / PRES ) ** E
E = 2. / 7. * ( 1 - ( .28 * .001 * MIXR ) )
TLCL = temperature at the LCL in Kelvin
MOISTURE PARAMETERS
DWPC - Dewpoint in Celsius
DWPF - Dewpoint in Fahrenheit
DWPK - Dewpoint in Kelvin
DPDC - Dewpoint depression in Celsius
DPDF - Dewpoint depression in Fahrenheit
DPDK - Dewpoint depression in Kelvin
MIXR - Mixing ratio in g/kg
MIXS - Saturated mixing ratio in g/kg
SMXR - Surface mixing ratio in g/kg
SMXS - Surface saturated mixing ratio in g/kg
RELH - Relative humidity in percent
TMWK - Wet bulb temperature in Kelvin
TMWC - Wet bulb temperature in Celsius
TMWF - Wet bulb temperature in Fahrenheit
VAPR - Vapor pressure in millibars
VAPS - Saturation vapor pressure in millibars
LHVP - Latent heat of vaporization in J/kg
PWTR - Precipitable water (mm) at any given level
DPDx = TMPx - DWPx
MIXR = .62197 * ( E / ( PRES - E ) ) * 1000
E = VAPR * [ 1.001 + ( PRES - 100) /
900 * .0034 ]
VAPR = 6.112 * EXP ( ( 17.67 * DWPC ) /
( DWPC + 243.5 ) )
MIXS = .62197 * ( Es / ( PRES - Es ) ) * 1000
Es = VAPS * [ 1.001 + ( PRES - 100 ) /
900 * .0034 ]
VAPS = 6.112 * EXP ( ( 17.67 * TMPC ) /
( TMPC + 243.5 ) )
SMXR = .62197 * ( E / ( PALT - E ) ) * 1000
E = VAPR * [ 1.001 + ( PALT - 100 ) /
900 * .0034 ]
VAPR = 6.112 * EXP ( ( 17.67 * DWPC ) /
( DWPC + 243.5 ) )
SMXS = .62197 * ( Es / ( PALT - Es ) ) * 1000
Es = VAPS * [ 1.001 + ( PALT - 100 ) /
900 * .0034 ]
VAPS = 6.112 * EXP ( ( 17.67 * TMPC ) /
( TMPC + 243.5 ) )
RELH = VAPR / VAPS * 100
( TMPK - TMWK ) * Cp - ( Rsat (TMWK) - RMIX ) * LVAP = 0
Implicit equation solved by Newton's method
for TMWK.
Cp - Specific heat at constant pressure
Rsat - Saturation mixing ratio at TMWK
RMIX - Mixing ratio
LVAP - Latent heat of vaporization
VAPR = 6.112 * EXP [ ( 17.67 * DWPC ) / ( DWPC + 243.5 ) ]
VAPS = 6.112 * EXP [ ( 17.67 * TMPC ) / ( TMPC + 243.5 ) ]
LHVP = ( 2.501 - .00237 * TMPC ) * 10E6
HEIGHT PARAMETERS
HGHT - Height in meters
HGTM - Height in meters
HGTK - Height in kilometers
HGTD - Height in decameters
HGFT - Height in feet (3.28084 * HGHT)
HGFH - Height in hundreds of feet
HGFK - Height in thousands of feet
HGML - Height in miles (6.2137E-04 * HGHT)
DHGT - Dry hydrostatic height in meters
MHGT - Moist hydrostatic height in meters
STDZ - Character standard height convention used on u.-a. charts
RSTZ - Numeric standard height convention used on u.-a. charts
For data below 500 mb, the standard height is the last three
digits of the height. For data at and above 500 mb, the
height is the last three digits of the height in decameters.
ZMSL, Z000, Z900, Z850, Z800 - Estimated height at a pressure
level
DHGT and MHGT are computed using the hypsometric
equation and integrating from the surface pressure
to the desired level. DHGT (MHGT) is computed
without (with) the influence of moisture.
DHGT = HB + ( RDGAS / G ) * LN ( PBOT / PTOP ) * TAVE
HB = height of the bottom of a layer
PBOT = pressure at bottom of a layer
PTOP = pressure at the top of a layer
TAVE = average temperature of a layer
MHGT = HB + ( RDGAS / G ) * LN ( PBOT / PTOP ) * TVAVE
HB = height of the bottom of a layer
PBOT = pressure at bottom of a layer
PTOP = pressure at the top of a layer
TVAVE = average virtual temperature of a layer
Zxxx = [ To * ( 1 - ( PRES / ALTM ) **
( RDGAS * GAMUSD / G ) ] / GAMUSD
Zxxx = height at the pressure level
ZMSL : 1013.25 mb
Z000 : 1000 mb
Z900 : 900 mb
Z850 : 850 mb
Z800 : 800 mb
To = sea level temperature in U.S. Std. Atmos.
= 288 K
PRESSURE AND ALTIMETER PARAMETERS
PRES - Station pressure in millibars
PRES is the actual pressure at a level as reported with
upper air data.
PMSL - Mean sea level pressure
PMSL is reported with surface data.
PALT - Surface pressure in millibars from ALTI
ALTI - Altimeter setting in inches of mercury
ALTI is reported with surface data.
ALTM - Altimeter setting converted to millibars
SALT - Abbreviated standard altimeter setting
SMSL - Abbreviated mean sea level pressure in millibars
SALI - Abbreviated altimeter setting in inches of mercury
RMSL - First 3 digits left of decimal of PMSL * 10
RSLI - First 3 digits left of decimal of ALTI * 100
RSLT - First 3 digits left of decimal of ALTM * 10
PTND - Pressure tendency: graphics symbol with numeric change
PTSY - Graphics symbol for pressure tendency
P03C - 3-h numeric pressure change
P03D - Pressure tendency and change group, appp
P24C - 24-h numeric pressure change
PMSL = PRES * EXP ( ( G * SELV ) / ( RDGAS * TVAVE ) )
SELV = station elevation
TVAVE = average virtual temperature between
station and sea level
= TVRK + ( DELTV / 2 )
DELTV = GAMUSD * SELV / 1000
PALT = ALTM *
( 1 - ( ( SELV / 1000 ) * GAMUSD / To ) ) **
( G / ( GAMUSD * RDGAS ) * 1000 )
SELV = station elevation in meters
To = sea level temperature in U.S. Std. Atmos.
= 288 K
ALTM = ALTI * ( 1013.25 / 29.921 )
SALT = MOD ( ALTM * 10, 1000 )
PANY - Returns PMSL, if avaliable, if not, returns ALTM
RANY - Computes the 3 digit display of pressure
SANY - Creates a 3 character string from integral part of PMSL or ALTM
WINDS
UWND - U-component of the wind in meters/second
VWND - V-component of the wind in meters/second
UKNT - U-component of the wind in knots
VKNT - V-component of the wind in knots
DRCT - Wind direction in degrees
SPED - Wind speed in meters/second
SKNT - Wind speed in knots
SMPH - Wind speed in miles/hour
PSPD - Packed direction and speed in meters/second (ddfff)
PKNT - Packed direction and speed in knots (ddfff)
GUST - Wind gusts in knots
GUMS - Wind gusts meters/second
PWDR - Peak 5-second wind direction in degrees
PWSP - Peak 5-second wind speed in meters/sec
PWHR - Hour of 5-second peak wind
PWMN - Minutes of 5-second peak wind
WNML - Wind component toward a direction 90 degrees counter-
clockwise from a specified direction.
WCMP - Wind component toward a specified direction
BARB - Barb feathered in m/s
BRBM - Barb feathered in m/s
BRBK - Barb feathered in knots
BRBS - Barb feathered in mi/hr
ARRW - Arrows scaled in m/s
ARRM - Arrows scaled in m/s
ARRK - Arrows scaled in knots
DARR - Wind direction arrows of uniform length
UWND = - SIN ( DRCT ) * SPED
VWND = - COS ( DRCT ) * SPED
DRCT = ATAN2 ( -UWND, -VWND ) * 180 / PI
SPED = SQRT ( UWND ** 2 + VWND ** 2 )
SPED = SKNT / 1.9438
PSPD = JDRCT * 100 + JSPED
JDRCT = NINT ( DRCT / 5 )
JSPED = NINT ( SPED )
PKNT = JDRCT * 100 + JSKNT
JDRCT = NINT ( DRCT / 5 )
JSKNT = NINT ( SKNT )
WCMP = - COS ( DRCT - SPCD ) * SPED
SPCD is the specified direction
WNML = - COS ( DRCT - ( SPCD - PI/2 ) ) * SPED
SPCD is the specified direction
LIFTED CONDENSATION LEVEL (LCL)
TLCL - Temperature in Kelvin at the LCL from the given level
PLCL - Pressure in millibars at the LCL from the given level
TLCL = [1 / ( 1 / ( DWPK - 56 ) +
LN ( TMPK / DWPK ) / 800 )] + 56
PLCL = PRES * ( TLCL / ( TMPC + 273.15 ) ) ** ( 1 / KAPPA )
Poisson's equation
STABILITY INDICES
Note: Default depths given in the definitions below are preceded
by an ! and may be changed using the in-line depth
specification. Negative depths reset to the default values.
Zero depth will yield missing values for layer parameters.
dz in the definitions below defaults to the layer thickness
in the sounding.
BRCH - Bulk Richardson number
BRCH = CAPE / ( 0.5 * U**2 )
CAPE = Convective Available Potential Energy
U = magnitude of shear ( u2 - u1, v2 - v1 )
u1,v1 = average u,v in the lowest !500 m
u2,v2 = average u,v in the lowest !6000 m
BRCV - BRCH computed by using CAPV
BRCH = CAPV / ( 0.5 * U**2 )
CAPV = CAPE computed by using virtual temperature
U = magnitude of shear ( u2 - u1, v2 - v1 )
u1,v1 = average u,v in the lowest !500 m
u2,v2 = average u,v in the lowest !6000 m
BVFQ - Brunt-Vaisala frequency in a layer
BVFQ = SQRT ( ( G / THTA ) * STAB )
BVPD - Brunt-Vaisala period in a layer
BVPD = 2. * PI / BVFQ
BVSQ - Brunt-Vaisala frequency squared in a layer
BVSQ = BVFQ ** 2
CAPE - Convective Available Potential Energy
CAPE = GRAVTY * SUMP ( DELZ * ( TP - TE ) / TE )
SUMP = sum over sounding layers from LFCT to
EQLV for which ( TP - TE ) is greater
than zero
DELZ = incremental depth
TP = temperature of a parcel from the lowest
!500 m of the atmosphere, raised dry
adiabatically to the LCL and moist
adiabatically thereafter
TE = temperature of the environment
CAPV - CAPE computed by using virtual temperature
CAPV = GRAVTY * SUMP ( DELZ * ( TVP - TVE ) / TVE )
SUMP = sum over sounding layers from LFCV to
EQTV for which ( TVP - TVE ) is greater
than zero
DELZ = incremental depth
TVP = virtual temperature of a parcel from the
lowest !500 m of the atmosphere, raised
dry adiabatically to the LCL and moist
adiabatically thereafter
TVE = virtual temperature of the environment
CINS - Convective Inhibition
CINS = GRAVTY * SUMN ( DELZ * ( TP - TE ) / TE )
SUMN = sum over sounding layers from top of the mixed
layer to LFCT for which ( TP - TE ) is less
than zero.
DELZ = incremental depth
TP = temperature of a parcel from the lowest
!500 m of the atmosphere, raised dry
adiabatically to the LCL and moist
adiabatically thereafter
TE = temperature of the environment
CINV - CINS computed by using virtual temperature
CINV = GRAVTY * SUMN ( DELZ * ( TVP - TVE ) / TVE )
SUMN = sum over sounding layers from top of the mixed
layer to LFCV for which ( TVP - TVE ) is less
than zero.
DELZ = incremental depth
TVP = virtual temperature of a parcel from the
lowest !500 m of the atmosphere, raised
dry adiabatically to the LCL and moist
adiabatically thereafter
TVE = virtual temperature of the environment
CTOT - Cross Totals index
CTOT = TD850 - T500
TD850 = Dewpoint in Celsius at 850 mb
T500 = Temperature in Celsius at 500 mb
EQLV - Equilibrium level
EQLV = level at which a parcel from the lowest !500 m of
the atmosphere is raised dry adiabatically to the
LCL and moist adiabatically to a level above which
the virtual temperature of the parcel is the same
as the environment. If more than one Equilibrium
Level exists, the highest one is chosen.
EQTV - EQLV computed by using virtual temperature
KINX - K index
KINX = ( T850 - T500 ) + TD850 - ( T700 - TD700 )
T850 = Temperature in Celsius at 850 mb
T500 = Temperature in Celsius at 500 mb
TD850 = Dewpoint in Celsius at 850 mb
T700 = Temperature in Celsius at 700 mb
TD700 = Dewpoint in Celsius at 700 mb
LAPS - Temperature lapse rate in a layer
LAPS = d (TMPK) / dz = d (TMPC) / dz
LCLP - Pressure in millibars at the LCL from the surface
LCLP = PRES * ( LCLT / ( TMPC + 273.15 ) ) ** ( 1 / KAPPA )
Poisson's equation
LCLT - Temperature in Kelvin at the LCL from the surface
LCLT = [1 / ( 1 / ( DWPK - 56 ) +
LN ( TMPK / DWPK ) / 800 )] + 56
LFCT - Level of Free Convection by comparing temperature between
a parcel and the environment
LFCT = level at which a parcel from the lowest !500 m of
the atmosphere is raised dry adiabatically to LCL
and moist adiabatically to the level above which
the parcel is positively buoyant. If more than
one LFCT exists, the lowest level is chosen. If
the parcel is positively bouyant throughout the
sounding, the LFCT is set to be the same as the
LCLP. If the parcel is negatively bouyant throughout
the sounding, the LFCT is set to missing.
LFCV - LFCT computed by using virtual temperature
LIFT - Lifted index
LIFT = T500 - Tparcel
T500 = temperature in Celsius of the environment
at 500 mb
Tparcel = 500 mb temperature in Celsius of a lifted
parcel with the average pressure,
temperature, and dewpoint of the layer
!100 mb above the surface
LFTV - LIFT computed by using virtual temperature
LHAN - Low elevation Haines Index
MHAN - Middle elevation Haines Index
HHAN - High elevation Haines Index
MLMR - Mean mixed layer MIXR
MLMR = average MIXR in the lowest !500 m
MLTH - Mean mixed layer THTA
MLTH = average THTA in the lowest !500 m
PWAT - Precipitable water (mm) for the entire sounding
RICH - Richardson number in a layer
RICH = BFVQ ** 2 / SHRM ** 2
SEPA - Isentropic pressure thickness in a layer
SEPA = pressure difference over a isentropic layer !5 K deep
SHOW - Showalter index
SHOW = T500 - Tparcel
T500 = Temperature in Celsius at 500 mb
Tparcel = Temperature in Celsius at 500 mb
of a parcel lifted from 850 mb
SHRD - Wind shear direction in a layer
SHRD = direction of [ du/dz, dv/dz ]
SHRM - Wind shear magnitude in a layer
SHRM = magnitude of [ du/dz, dv/dz ]
STAB - THTA lapse rate in a layer
STAB = d (THTA) / dz
STAP - THTA change with pressure in a layer
STAP = - d (THTA) / dp
SWET - SWEAT index
SWET = 12 * TD850 + 20 * TERM2 + 2 * SKT850 +
SKT500 + SHEAR
TD850 = Dewpoint in Celsius at 850 mb
TERM2 = MAX ( TOTL - 49, 0 )
TOTL = Total totals index
SKT850 = 850 mb wind speed in knots
SKT500 = 500 mb wind speed in knots
SHEAR = 125 * [ SIN ( DIR500 - DIR850 ) + .2 ]
DIR500 = 500 mb wind direction
DIR850 = 850 mb wind direction
If TD850 is negative, then TD850 is set to 0.
SHEAR is set to 0 if any of the following
conditions are met:
wind direction at 850mb is < 130 or > 250
wind direction at 500mb is < 210 or > 310
DIR500 - DIR850 <= 0
SPD500 <= 15 or SPD850 <= 15
TOTL - Total Totals index
TOTL = ( T850 - T500 ) + ( TD850 - T500 )
T850 = Temperature in Celsius at 850 mb
TD850 = Dewpoint in Celsius at 850 mb
T500 = Temperature in Celsius at 500 mb
VTOT - Vertical Totals index
VTOT = T850 - T500
T850 = Temperature in Celsius at 850 mb
T500 = Temperature in Celsius at 500 mb
CLOUD PARAMETERS
Cloud coverage may be defined using a cloud code, short code,
fractional coverage or numeric value. The valid values of these
parameters ordered from least to greatest cloud coverage, are:
Cloud Coverage Cloud Short Fractional Numeric Symbol
xCLD xCLO CLCx CFRT
missing - 0.00 0 -
clear CLR C 0.00 1 0
thin scattered -SCT -S 0.25 6 2
scattered SCT S 0.40 2 3
thin broken -BKN -B 0.60 7 5
broken BKN B 0.75 3 6
thin overcast -OVC -O 0.90 8 7
overcast OVC O 1.00 4 8
thin obscured -X -X 0.00 9 0
obscured X X 1.00 5 9
The following lists the GEMPAK parameter definitions with an
example using the sample AIRWAYS cloud report:
22SCT 80-BKN 250OVC
Note that the character x may be replaced by L, M, or H,
indicating low, mid or high clouds. Also note that the
character T indicates the value of the parameter at the level
of maximum cloud coverage.
xCLD - Character cloud coverage code
Examples: LCLD = SCT
MCLD = -BKN
HCLD = OVC
TCLD - xCLD at maximum cloud coverage
Example: TCLD = OVC
xCLO - Fractional cloud coverage
Examples: LCLO = 0.400
MCLO = 0.600
HCLO = 1.000
TCLO - xCLO at maximum cloud coverage
Example: TCLO = 1.00
CLCx - Numeric cloud coverage
Examples: CLCL = 2
CLCM = 7
CLCH = 4
CLCT - CLCx at maximum cloud coverage
Example: CLCT = 4
The next two parameters combine cloud coverage values from the
three cloud levels.
CLDS - Combined cloud coverage short code from three levels
Example: CLDS = S-BO
CMBC - Combined cloud coverage numeric from three levels
Example: CMBC = 274
The next set of parameters are combined cloud height and
cloud coverage.
CLHx - Cloud height in hundreds of feet
Examples: CLHL = 22.
CLHM = 80.
CLHH = 250.
CLDx - Combined cloud height and short code
Examples: CLDL = 22S
CLDM = 80-B
CLDH = 250O
CLDT - CLDx at maximum coverage level
Example: CLDT = 250O
CLDB - CLDx at the lowest ceiling/layer
Example: CLDB = 22S
COMx - Numeric combined cloud height and coverage combined as
CLHx * 10 + CLCx
Examples: COML = 222.
COMM = 807.
COMH = 2504
Note: In the case when the sky is partially obscured, the
value of 10000 is added on to the lowest reporting level.
For example, if AIRWAYS report is -X M5 BKN 19 BKN,
COML would equal 10053.
COMT - COMx at maximum coverage level
Example: COMT = 2504.
The next two parameters combine the cloud height and coverage
allowing up to three reports which do not necessarily correspond
to low, middle and high level clouds. These parameters allow a
means of storing cloud reports where there may be more than
one report at a single level.
CHCx - Numeric combined cloud height and coverage combined as
CLHx * 10 + CLCx, where x is the cloud report group
number from 1 to 3.
Examples: CHC1 = 222.
CHC2 = 807.
CHC3 = 2504
Note: In the case when the sky is partially obscured, the
value of 10000 is added on to the first reporting level.
For example, if AIRWAYS report is -X M5 BKN 19 BKN,
CHC1 would equal 10053.
CHDx - Combined cloud height and short code
Examples: CHD1 = 22S
CHD2 = 80-B
CHD3 = 250O
The next parameter is the ceiling, defined as the height above
the earth's surface of the lowest cloud layer that is reported
as broken or overcast, or the vertical visibility into an
indefinite ceiling.
CEIL - Ceiling in hundreds of feet
The following set of cloud parameters is the numeric WMO codes
which are reported by airways data.
CFRL - Fraction of celestial dome covered by all low and mid
level clouds from WMO Code 2700
CTYL - Low-level cloud genera from WMO Code 0513
CTYM - Mid-level cloud genera from WMO Code 0515
CTYH - High-level cloud genera from WMO Code 0509
CBAS - Cloud base height from WMO Code 1600
CSYL - Cloud graphics symbol for CTYL
CSYM - Cloud graphics symbol for CTYM
CSYH - Cloud graphics symbol for CTYH
CSYT - Cloud graphics symbol for first level reporting clouds
CFRT - Cloud coverage number from CLCT (maximum clouds)
SKYC - Cloud coverage graphics symbol for CFRT
SKYM - Sky coverage symbol with wind barbs in m/s
SKYK - Sky coverage symbol with wind barbs in knots
XVFR - Categorical identification of flight rules
0 = Low Instrument Flight Rules (LIFR)
1 = Instrument Flight Rules (IFR)
2 = Marginal Visual Flight Rules (MVFR)
3 = Visual Flight Rules (VFR)
The flight categories and corresponding ceiling and visibility
values are listed below.
Flight CEILING VISIBILITY
Category (feet) (statute miles)
===============================================================
LIFR < 500 ft and/or < 1 SM
IFR >= 500 to < 1,000 and/or >= 1 to < 3
MVFR >= 1,000 to <= 3,000 and/or >= 3 to <= 5
VFR > 3,000 or none and > 5
===============================================================
WEATHER CODES
WCOD - Character weather code
WNUM - Numeric weather code
The weather code WCOD may also be accessed as WTHR. The
weather number consists of 3 parts, A, B, C where
WNUM = A * 80 * 80 + B * 80 + C.
Each part corresponds to one of the values:
0 (no value)
1 R (mod rain) 41 UP (unknown prcp)
2 L (mod drizzle) 42
3 S (mod snow) 43
4 A (mod hail) 44
5 T (thunder) 45
6 H (haze) 46
7 K (smoke) 47
8 D (dust) 48
9 F (fog) 49 ZR- (lt frz rain)
10 Q (squalls) 50 ZR+ (hvy frz rain)
11 V (volcanic ash) 51 RW- (lt rain shwr)
12 52 RW+ (hvy rain shwr)
13 R- (lt rain) 53 ZL- (lt freezing drizzle)
14 R+ (hvy rain) 54 ZL+ (hvy freezing drizzle)
15 ZR (mod frz rain) 55 SW- (lt snow shwr)
16 RW (mod rain shwr) 56 SW+ (hvy snow shwr)
17 L- (lt drizzle) 57 IP- (lt ice pellets)
18 L+ (hvy drizzle) 58 IP+ (hvy ice pellets)
19 ZL (frz drizzle) 59 SG- (lt snow grains)
20 S- (lt snow) 60 SG+ (hvy snow grains)
21 S+ (hvy snow) 61 SP- (lt snow pellets)
22 SW (mod snow shwr) 62 SP+ (hvy snow pellets)
23 IP (mod ice pellet) 63 IPW (mod ice pellet shwr)
24 SG (mod snow grain) 64 IC- (lt ice crystals)
25 SP (mod snow pellet) 65 IC+ (hvy ice crystals)
26 A- (lt hail) 66 TRW (mod thunder shwr)
27 A+ (hvy hail) 67 SPW (snow pellet shwr)
28 T- (lt thunder) 68 BD+ (hvy blowing dust)
29 T+ (hvy thunder) 69 BN+ (hvy blowing sand)
30 IF (ice fog) 70 BS+ (hvy blowing snow)
31 GF (ground fog) 71
32 BS (blowing snow) 72
33 BD (blowing dust) 73
34 BY (blowing spray) 74
35 BN (blowing sand) 75 IPW- (lt ice pellet shwr)
36 IC (mod ice crystals) 76 IPW+ (hvy ice pellet shwr)
37 IN (ice needles) 77 TRW- (lt rain thunder shwr)
38 AP (small hail) 78 TRW+ (hvy rain thunder shwr)
39 KH (smoke, haze) 79
40 PO (dust whirls)
The following correspond to a single character code:
-1 TORNA (tornado) -3 WATER (water spout)
-2 FUNNE (funnel cloud)
WNUM - Numeric weather code, as computed from the METAR codes
The weather number consists of 3 parts, A, B, C where
WNUM = A * 80 * 80 + B * 80 + C.
Each part corresponds to one of the values:
-1 +FC (tornado or -2 FC (funnel cloud)
waterspout)
0 (no value)
1 RA (mod rain) 41 UP (unknown prcp)
2 DZ (mod drizzle) 42
3 SN (mod snow) 43
4 GR (mod hail) 44
5 TS (thunder) 45
6 HZ (haze) 46
7 FU (smoke) 47
8 DU (dust) 48
9 FG (fog) 49 -FZRA (lt frz rain)
10 SQ (squalls) 50 +FZRA (hvy frz rain)
11 VA (volcanic ash) 51 -SHRA (lt rain shwr)
12 52 +SHRA (hvy rain shwr)
13 -RA (lt rain) 53 -FZDZ (lt frz drizzle)
14 +RA (hvy rain) 54 +FZDZ (hvy frz drizzle)
15 FZRA (mod frz rain) 55 -SHSN (lt snow shwr)
16 SHRA (mod rain shwr) 56 +SHSN (hvy snow shwr)
17 -DZ (lt drizzle) 57 -PL (lt ice pellets)
18 +DZ (hvy drizzle) 58 +PL (hvy ice pellets)
19 FZDZ (frz drizzle) 59 -SG (lt snow grains)
20 -SN (lt snow) 60 +SG (hvy snow grains)
21 +SN (hvy snow) 61 -GS (lt snow pellets)
22 SHSN (mod snow shwr) 62 +GS (hvy snow pellets)
23 PL (mod ice pellet) 63 SHPL (mod ice pellet shwr)
24 SG (mod snow grain) 64
25 GS (mod snow pellet) 65
26 66 TSRA (mod thunder shwr)
27 SHGR (hvy hail) 67 SHGS (snow pellet shwr)
28 68 +BLDU (hvy blowing dust)
29 69 +BLSA (hvy blowing sand)
30 FZFG (ice fog) 70 +BLSN (hvy blowing snow)
31 BR (ground fog) 71
32 BLSN (blowing snow) 72
33 BLDU (blowing dust) 73
34 BLPY (blowing spray) 74
35 BLSA (blowing sand) 75 -SHPL (lt ice pellet shwr)
36 IC (mod ice crystals) 76 +SHPL (hvy ice pellet shwr)
37 77 -TSRA (lt rain thunder shwr)
38 78 +TSRA (hvy rain thunder shwr)
39 79
40 PO (dust whirls)
WTMO - Character WMO weather code
WWMO - Numeric WMO weather code
WSYM - Graphics weather symbol corresponding to WWMO
The transformation is:
0 = 34 = BD+ 67 = ZR
1 = 35 = BD+ 68 = R-S-
2 = 36 = BS 69 = RS
3 = 37 = BS+ 70 = S-
4 = K 38 = BS 71 = S-
5 = H 39 = BS+ 72 = S
6 = D 40 = 73 = S
7 = BD 41= F 74 = S+
8 = PO 42 = F 75 = S+
9 = 43 = F 76 = IN
10 = F 44 = F 77 = SG
11 = GF 45 = F 78 = IC
12 = GF 46 = F 79 = IP
13 = 47 = F 80 = RW-
14 = 48 = IF 81 = RW
15 = 49 = IF 82 = RW+
16 = 50 = L- 83 = RW-SW-
17 = T 51 = L- 84 = RWSW
18 = Q 52 = L 85 = SW-
19 = FUNNE 53 = L 86 = SW
20 = 54 = L+ 87 = IPW-
21 = 55 = L+ 88 = IPW
22 = 56 = ZL- 89 = A-
23 = 57 = ZL 90 = A
24 = 58 = R-L- 91 = R-
25 = 59 = RL 92 = R
26 = 60 = R- 93 = RS
27 = 61 = R- 94 = R+S+
28 = 62 = R 95 = TRW-
29 = 63 = R 96 = TRW-A
30 = BD 64 = R+ 97 = TRW+
31 = BD 65 = R+ 98 = TD
32 = BD 66 = ZR- 99 = TRW+A
33 = BD+
105 = TSW- 107 = TSW+
201 = V 202 = BY 203 = UP
PWTH - Character past weather WMO code or graphics symbol for it
PWWM - Numeric past weather WMO code
The past weather WMO numeric codes are:
0 = Cloud covering less than 1/2 sky
1 = Cloud covering more than 1/2 during part of
period and less than 1/2 sky during part
2 = Cloud covering more than 1/2 sky
3 = Sandstorm, duststorm or blowing snow
4 = Fog, ice fog, thick haze or thick smoke
5 = Drizzle
6 = Rain
7 = Snow, rain and snow mixed or ice pellets
8 = Showers
9 = Thunderstorm with or without precipitation
The translation is:
0 = 5 = L
1 = 6 = R
2 = 7 = S
3 = BD 8 = RW
4 = F 9 = T
STATION PARAMETERS
STID - Character station identifier
STNM - Station number
STNM is the 5-digit WMO identifier for upper air data; 6
digits for surface data, usually the WMO identifier with a
zero appended.
SLAT - Station latitude in degrees
SLON - Station longitude in degrees; West longitude is negative
SELV - Station elevation in meters
RANG - Range in kilometers (specialized use)
AZIM - Azimuth in kilometers (specialized use)
LATI - Latitude in degrees from range/azimuth
LONG - Longitude in degrees from range/azimuth
LATI and LONG are calculated from the RANG and AZIM using
equations developed for AOIPS/RADPAK.
DELT - Delta time in seconds (specialized use)
MODEL OUTPUT STATISTICS
MXMN - Maximum or minimum temperature in Fahrenheit
TNTF - Night temperature fcst in Fahrenheit
TNCF - Night temperature climatology in Fahrenheit
TNAF - Night temperature anomaly in Fahrenheit
TDYF - Day temperature fcst in Fahrenheit
TDCF - Day temperature climatology in Fahrenheit
TDAF - Day temperature anomaly in Fahrenheit
CL12 - Prevailing total sky cover fcst for a 12-hr period
1 = CL = mostly clear
4 = OV = mostly overcast
7 = PC = mixed clouds and clear skies
SK12 - Maximum sustained surface wind speed fcst for a 12-hr period
5 = light = 0 - 12 knots
15 = moderate = 13 - 21 knots
25 = strong = 22 - 33 knots
40 = high = greater than or equal to 34 knots
PP06 - Probability of precipitation fcst in a 6-hr period
PP12 - Probability of precipitation fcst in a 12-hr period
PP1C - Probability of precipitation climatology in a 12-hr period
PP1A - Probability of precipitation anomaly in a 12-hr period
PP24 - Probability of precipitation fcst in a 24-hr period
PP2C - Probability of precipitation climatology in a 24-hr period
PP2A - Probability of precipitation anomaly in a 24-hr period
QP06 - Quantitative precipitation fcst in a 6-hr period
1 = 0.01 - 0.09 inches
2 = 0.10 - 0.24 inches
3 = 0.25 - 0.49 inches
4 = 0.50 - 0.99 inches
5 = 1.00 - 1.99 inches
QPX2 - Maximum amount of precipitation in inches fcst in a 12-hr
period. Values are same as QP12.
QP12 - Quantitative precipitation fcst in a 12-hr period
0 = no precipitation expected
1 through 5 same as QP06
6 = greater than or equal to 2.00 inches
QP24 - Quantitative precipitation fcst in a 24-hr period
0 through 5 same as QP12
6 = 2.00 - 2.99 inches
7 = greater than or equal to 3.00 inches
TS06 - Unconditional probability of thunderstorms occurring
in a 6-hr period
TS12 - Unconditional probability of thunderstorms occurring
in a 12-hr period
TS24 - Unconditional probability of thunderstorms occurring
in a 24-hr period
TC06 - Conditional probability of severe weather occurring
in a 6-hr period
TC12 - Conditional probability of severe weather occurring
in a 12-hr period
PCPT - Categorical forecast of precipitation
0 = R = rain
1 = S = snow
2 = Z = freezing
POZP - Conditional probability of freezing precipitation
(not included during the warm season)
POSN - Conditional probability of snow
(not included during the warm season)
SN06 - Categorical forecast of snow amount falling in a 6-hr
period
0 = no snow
1 = trace to less than 2 inches
2 = greater than or equal to 2 inches
SN12 - Categorical forecast of snow amount falling in a 12-hr
period
0 and 1 same as SN06
2 = 2 to less than 4 inches
4 = 4 to less than 6 inches
6 = greater than 6 inches
(not included during the warm season)
SN24 - Categorical forecast of snow amount falling in a 24-hr
period
0 = no snow or a trace
1 = greater than a trace to less than 2 inches
2 = 2 to less than 4 inches
4 = 4 to less than 6 inches
6 = 6 to less than 8 inches
8 = greater than 8 inches
(not included during the warm season)
PZ12 - Conditional probability of freezing precipitation in a 12-hr
period
PS12 - Conditional probability of snow in a 12-hr period
PR12 - Conditional probability of mixed liquid/frozen precipitation
in a 12-hr period
PC12 - Categorical forecast of precipitation type in a 12-hr period
0 = R = liquid
1 = S = frozen
2 = Z = freezing
3 = RS = mixed liquid and frozen precipitation
4 = RZ
5 = SZ
6 = RSZ
FCIG - Categorical forecast of ceiling height conditions
1 = less than 200 feet
2 = 200 - 400 feet
3 = 500 - 900 feet
4 = 1000 - 1900 feet
5 = 2000 - 3000 feet
6 = 3100 - 6500 feet
7 = 6600 - 12,000 feet
8 = greater than 12,000 feet or unlimited
FVIS - Categorical forecast of visibility conditions
1 = less than 0.5 miles
2 = 0.5 - 0.875 miles
3 = 1.0 - 2.75 miles
4 = 3.0 - 5.0 miles
5 = greater than 5.0 miles
FVSA - Categorical forecast of visibility conditions (for new MOS)
1 = less than 0.5 miles
2 = 0.5 mile to less than 1.0 mile
3 = 1.0 to less than 2.0 miles
4 = 2.0 to less than 3.0 miles
5 = 3.0 to 5.0 miles
6 = 6.0 miles
7 = greater than 6.0 miles
OVIS - Categorical forecast in plain language of obstructions
to vision
0 = N = none of the following:
1 = FG or F = fog or ground fog (vis. less than .625 mile)
2 = HZ or H = haze, smoke, dust
3 = BR = mist (fog with visibility greater than .625 mile)
4 = BL = blowing dust, sand, snow
WXPB - Categorical weather precipitation probability or areal coverage
determined by the precipitation parameter having the highest
probability or areal coverage in WNUM.
For probability:
1 = slight chance
2 = chance
3 = likely
4 = occasional
5 = definite
For areal coverage:
1 = isolated
2 = widely scattered
3 = scattered
4 = numerous
5 = widespread
TERMINAL AERODROME FORECAST (TAF) PARAMETERS
TDRC - Temporary/probability wind direction in degrees
TSKN - Temporary/probability wind speed in knots
TGST - Temporary/probability wind gusts in knots
BRGK - Gust barb feathered in knots
TCHx - Temporary/probability numeric combined cloud height and
coverage, as for CHCx
TCEL - Temporary/probability ceiling in hundreds of feet, as for CEIL
TSKC - Temporary/probability cloud coverage graphics symbol, as for
SKYC
TXVF - Temporary/probability categorical identification of flight
rules, as for XVFR
TWNM - Temporary/probability numeric weather code, as for WNUM
TWSY - Temporary/probability graphics weather symbol corresponding to
TWNM, as for WSYM
TVSB - Temporary/probability visibility in statute miles
PPRB - Probability for TAF forecast change indicator
30 = PROB30 - 30 percent probability condition
40 = PROB40 - 40 percent probability condition
50 = TEMPO - temporary condition
VWNM - Vicinity numeric weather code, as for WNUM
VWSY - Vicinity graphics weather symbol corresponding to VWNM, as for
WSYM
TVWN - Temporary/probability vicinity numeric weather code, as for
WNUM
WSKC - Worst case cloud coverage graphics symbol, as for SKYC
WXVF - Worst case categorical identification of flight rules, as for
XVFR
TPWN - Temporary/probability/vicinity numeric weather code, as for
WNUM
TPWS - Temporary/probability/vicinity graphics weather symbol
corresponding to TPWN, as for WSYM
AWNM - Prevailing/temporary/probability/vicinity numeric weather code,
as for WNUM
AWSY - Prevailing/temporary/probability/vicinity graphics weather
symbol corresponding to AWNM, as for WSYM
LLWS - Low level wind shear forecast flag
MOTV - Mountain obscuration threshold value in hundreds of feet
CMSL - Ceiling converted to mean sea level in hundreds of feet
MOBS - Mountain obscuration threshold met indicator
TCMS - Temporary/probability ceiling converted to mean sea level in
hundreds of feet
TMOB - Temporary/probability mountain obscuration threshold met
indicator
WCMS - Worst case ceiling converted to mean sea level in hundreds of
feet
WMOB - Worst case mountain obscuration threshold met indicator
TCTL - Temporary/probability low-level cloud genera from WMO Code
0513, as for CTYL
TCSL - Temporary/probability cloud graphics symbol for TCTL, as for
CSYL
MARINE PARAMETERS
WHGT - Wave height in meters
WHFT - Wave height in feet
WPER - Wave period in seconds
HOWW - Height of wind wave in meters
POWW - Period of wind wave in seconds
HOSW - Height of predominant swell wave in meters
POSW - Period of predominant swell wave in seconds
DOSW - Direction of predominant swell wave in degrees
HOS2 - Height of secondary swell wave in meters
POS2 - Period of secondary swell wave in seconds
DOS2 - Direction of secondary swell wave in degrees
WAV2 - Combined wind wave period and height in feet ("2 group")
WAV3 - Combined predominant and secondary swell wave direction
in tens of degrees ("3 group")
WAV4 - Combined predominant swell wave period and height in
feet ("4 group")
WAV5 - Combined secondary swell wave period and height in feet
("5 group")
WPHM - Combined wave period and height in half meters
WVSW - Combined swell wave direction, period and height in half
meters
SWEL - Character combined swell wave direction, period and
height in half meters
DAWV - Swell wave direction arrows of uniform length
IDTH - Thickness of ice on ship in meters
ROIA - Rate of ice accretion on ship from WMO Code 3551
0 = Ice not building up
1 = Ice building up slowly
2 = Ice building up rapidly
3 = Ice melting or breaking up slowly
4 = Ice melting or breaking up rapidly
IGRO - Rate of ice accretion on vessel in salt water in inches per
three hours
IGRO = ( A*PR + B*PR*PR + C*PR*PR*PR ) * CVFAC
A = 2.73 * 10E-2
B = 2.91 * 10E-4
C = 1.84 * 10E-6
PR = ( SPED * ( -1.7 - TMPC ) ) /
( 1 + 0.4 * ( SSTC + 1.7 ) )
(priesendorfer regression)
CVFAC = 1.1811, to convert cm/hr to in/3hr
DIGR - Character rate of ice accretion in inches per three hours
SHPD - True direction from which ship is moving (for 3 hours before
obs) in degrees
SHPK - Ship's average speed (for 3 hours before obs) in knots
DASH - Ship's true direction arrows of uniform length
PMN1 - Lowest 1-minute average pressure in previous hour in mb
PMNT - Time of lowest 1-minute average pressure, as hhmm
PKWD - Direction of 1-minute peak wind in previous hour in degrees
PKWK - Highest 1-minute mean wind speed in previous hour in knots
PKWS - Highest 1-minute mean wind speed in previous hour in m/sec
PKWT - Time of highest peak 1-minute wind in previous hour, as hhmm
BRPK - Wind barb (knots) for highest peak 1-minute wind
AIRCRAFT PARAMETERS
TURB - Amount of turbulence
0 = No turbulence
2 = Light turbulence
3 = Light to moderate turbulence
4 = Moderate turbulence
5 = Moderate to severe turbulence
6 = Severe turbulence
8 = Extreme turbulence
TBSE - Base of turbulence in feet
TTOP - Top of turbulence in feet
HBOT - Base of turbulence in meters
HTOT - Top of turbulence in meters
FQOT - Frequency of turbulence
1 = Occasional
2 = Intermittent
3 = Continuous
TPOT - Type of turbulence
1 = Clear air turbulence
2 = Chop
3 = Low level wind shear
4 = Turbulence in cloud
TBSY - Graphics symbol for turbulence
ICNG - Amount of airframe icing
0 = No icing
1 = Trace icing
2 = Trace to light icing
3 = Light icing
4 = Light to moderate icing
5 = Moderate icing
7 = Moderate to severe icing
8 = Severe icing
IBSE - Base of icing in feet
ITOP - Top of icing in feet
HBOI - Base of icing in meters
HTOI - Top of icing in meters
TPOI - Type of icing
1 = Rime
2 = Clear
3 = Mixed
4 = Rime in cloud
5 = Clear in cloud
6 = Mixed in cloud
7 = Rime in precipitation
8 = Clear in precipitation
9 = Mixed in precipitation
10 = Frost
11 = Non-persistent contrails
12 = Persistent contrails
ICSY - Graphics symbol for icing
WBSE - Base of weather in feet
WTOP - Top of weather in feet
HBWX - Base of weather in meters
HTWX - Top of weather in meters
CLC1 - Numeric cloud coverage 1
CBS1 - Cloud base 1 in feet
CTP1 - Cloud top 1 in feet
CB1M - Cloud base 1 in meters
CT1M - Cloud top 1 in meters
CLC2 - Numeric cloud coverage 2
CBS2 - Cloud base 2 in feet
CTP2 - Cloud top 2 in feet
CB2M - Cloud base 2 in meters
CT2M - Cloud top 2 in meters
ACRT - Aircraft report type
1 = AIREP - Aircraft report
2 = PIREP - Pilot report
3 = RECCO - Reconnaissance flight report
4 = AMDAR - Aircraft report (aircraft meteorological
data relay)
SELV - Flight level in meters
FELV - Flight level in hundreds of feet
ITSY - Icing type symbol
TTSY - Turbulence type symbol
TFSY - Turbulence frequency symbol
ACTP - Character aircraft type
ATP1 - Numeric aircraft type
The numeric aircraft type is a real representation of
up to four characters from the character aircraft type.
ATP1 = v4 * 40 * 40 * 40 + v3 * 40 * 40 + v2 * 40 + v1.
Each character corresponds to one of the values:
1 = - 9 = 5 17 = D 25 = L 33 = T
2 = . 10 = 6 18 = E 26 = M 34 = U
3 = / 11 = 7 19 = F 27 = N 35 = V
4 = 0 12 = 8 20 = G 28 = O 36 = W
5 = 1 13 = 9 21 = H 29 = P 37 = X
6 = 2 14 = A 22 = I 30 = Q 38 = Y
7 = 3 15 = B 23 = J 31 = R 39 = Z
8 = 4 16 = C 24 = K 32 = S
Any character not defined above is treated as a /.
MISCELLANEOUS PARAMETERS
VSBY - Visibility in statute miles
VSBK - Visibility in kilometers
VSBN - Visibility in nautical miles
VSBF - Character visibility in fractions of statute miles for
visibilities between 0. and 1.
VSBC - Character visibility in fractions of statute miles for
all visibility numbers
PnnI - Precipitation over last nn hours in inches
nn = 01, 03, 06, 09, 12, 18 or 24
PnnM - Precipitation over last nn hours in millimeters
nn = 01, 03, 06, 09, 12, 18 or 24
DPRC - Character daily weather map precipitation in inches
PR24 - Precipitation over last 24 hours in inches, as sum of
four successive 6-hour precip amounts
SNOW - Snow depth in inches
SNEW - Amount of new snow in inches
SNRT - Forecast snow and ice pellet accumulation to watch
threshold ratio
SI12 - Forecast snow and ice pellet 12-h accumulation in inches
SNIP - Snow and ice pellet watch threshold in inches
FZRT - Forecast freezing rain accumulation to watch threshold
ratio
FZ12 - Forecast Freezing rain 12-h accumulation in inches
FZRN - Freezing rain watch threshold in inches
WEQS - Water equivalent of snow on the ground in inches
HAIL - Hail flag
HLSZ - Hail size in centimeters
DDEN - Density of dry air in kg/(m**3)
PSYM - Montgomery stream function in m**2/(100*s**2)
HEAT - Heat index in Fahrenheit
HMTR - Humiture (apparent temperature) in Fahrenheit
WCEQ - Wind chill equivalent temperature in Fahrenheit
WCHT - Revised wind chill temperature in Fahrenheit
MSUN - Duration of sunshine in minutes
FFnn - Flash flood guidance for next nn hours in inches
nn = 01, 03, 06, 12 or 24
TOST - Type of station (manned or automatic)
0 = automatic
1 = manned
STIM - Report hour and minutes as hhmm
TEXT - Undecoded data
SPCL - Undecoded special reports
MARK - Markers
FOSB - Fosberg Index, also called Fire Weather Index
SPACING PARAMETERS
BLNK - Plot a blank, not accounted for in FILTER
SPAC - Plot a space, accounted for in FILTER